What P0A42 means
P0A42 is the counterpart to P0A41: a resolver line of motor A reads above its allowed range.
How the engine computer detects it
Typical triggers are a sine, cosine or excitation wire shorted to a supply voltage, or an open coil whose line is pulled up by the bias resistors of the input circuit, which drives the converter into clipping. Kia covers it in the same Optima Hybrid 2011-13 bulletin as P0A41: intermittent MIL or hybrid service lamp, fixed by inspecting the HPCU-to-motor sub-harness for internal shorts and pin fit. Bosch patents explain why clipping alone is not enough and how the line offset reveals a short to supply or an open line. P0A3F is the general circuit fault. Expect a warning lamp and reduced or no electric drive.
Written from public technical sources and not yet checked by a mechanic. How we write these pages
Symptoms
- Intermittent MIL or hybrid service lamp
- Electric drive disabled or vehicle not ready
- Reduced power until the fault clears
Common causes
- Resolver wire shorted to a supply voltage inside the sub-harness (Kia Optima Hybrid) Most likely
- Open sine or cosine line pulled high by the input circuit Possible
- Poor pin fit or corrosion at the resolver connectors Possible
- Faulty resolver input stage in the motor control unit Less likely
How to diagnose P0A42
- Read every stored code with an OBD-II scanner. If misfire or fuel trim codes are there too, fix those first: they often cause this one.
- Inspect the parts involved: drive motor a position sensor, wiring harness, hybrid control module.
- Work through the causes above from most to least likely, cheapest checks first.
- Clear the code and drive a full drive cycle to confirm the repair held.
Reading the code
- P
- Powertrain
- 0
- Generic (SAE) code
- A
- Hybrid and electric propulsion
- 42
- Specific fault
Questions drivers ask
Can I drive with code P0A42?
If the car drives normally, drive gently to a shop that services hybrids. If it shows a hybrid system warning, loses power or won't go into Ready, pull over and have it towed. Never touch orange high-voltage cables.
Will my car pass an emissions inspection with P0A42?
Probably not in states that test vehicles with an OBD-II scan: an emissions-related code that keeps the check engine light on is usually an automatic fail. Rules differ by state and county, so check yours.
This page is general information, not a substitute for a professional diagnosis. Repair costs are rough estimates for parts and labor and vary by vehicle and region.